Within this research program studies will be conducted in the following broad areas of research: (a) prenatal influences on postnatal growth and development and on psychological and physiological processes; (b) investigations of maternal and neonatal factors on physiological and behavioral development; (c) psychobiology of lactation; and (d) influence of hormones on adult behavior. The first series of studies on prenatal effects will investigate the role of prenatal influences on growth and development and adult behavioral and physiological functions. The two major procedures will be the use of ova transplants to study the influence of intrauterine environments, and the manipulation of maternal fetal-hormonal relationships to determine the influence of these hormones prenatally on subsequent development and function. In the second series of studies related to postnatal factors we propose to investigate the influence of early experience and alterations of mother- infant relationships on coping behavior in the rat, and to extend our investigations to study the effects of isolation and mother- infant separation in both squirrel monkeys and Rhesus macaques on subsequent neuroendocrine activity and behavior. The studies on the effects of lactation and its influence on the pituitary-adrenal response to stress and on behavior will also be continued. Studies on the role of fetal and neonatal gonadal hormones in sexual differentiation will be extended to the squirrel monkey. These investigations will initially focus on the influence of these hormones on sex dimorphic behaviors in the prepubertal animal. Finally, parametric studies of pituitary-adrenal activity in the squirrel moneky will provide the bases for studying the influence of these hormones on behavior and will also provide the bases for studying various coping strategies on the modulation of neuroendocrine activity related to the pituitary-adrenal.